The invention, as more fully described hereinafter, relates to an anisotropically electrically conductive composition, such as a gel, having the further attribute of being able to isotropically conduct heat.
Electrically conductive compositions, such as gels or adhesives, have become recognized systems for electrically interconnecting conductive areas or conductors on a pair of substrates. By way of example, polymeric electrically conductive materials, such as conductive epoxies and thermoplastic adhesives, have been used to establish interconnections for electrical circuitry. Conductive epoxies have been employed to mount electrical components on printed circuit boards. Polymeric electrically conductive adhesives have also been employed in tape form to interconnect conductors on a substrate with other components or circuitry. When used to establish such electrical interconnections, these conductive epoxies and conductive adhesives can be deposited on a surface in a conventional manner, such as by screen printing. Then upon the application of heat and pressure or upon the application of pressure, depending upon the precise character of the conductive adhesive, both electrical and structural or mechanical integrity can be established between separate conductors. For more information on conductive gel interconnection systems, see U.S. Pat. No. 4,770,641 to Rowlette.
Conductive adhesives, as more fully described in U. S. Pat. No. 4,729,809 to Dery et al, comprise a mixture of conductive particles in a nonconductive adhesive binder. Dery et al is specifically directed to an anisotropically conductive adhesive which will permit electrical conductivity normal to the plane of the substrate to which the adhesive has been applied, while precluding conductivity between adjacent conductive areas in the plane of the substrate. By way of brief reference, insofar as electrical interconnection devices are concerned, a gel may be described as a disconnectable composition, whereas an adhesive is non-disconnectable.
U.S. Pat. No. 4,170,677 to Hutcheon discloses an earlier version-of an anisotropically conductive adhesive composition. This disclosure reveals the use of whisker-like particles which are either paramagnetic or ferromagnetic. Once the adhesive is coated on a substrate, the substrate must be exposed to a magnetic or electrical field to make the conductive whiskers align perpendicular to the substrate. The adhesive must then be hardened while the field is still applied.
U.S. Pat. No. 4,252,391 to Sado discloses a method for preparing. anisotropically pressure-sensitive electroconductive composite sheets. These sheets are comprised of electrically conductive fibers that have been distributed in a matrix of an electrically insulating substance. The fibers are aligned in a direction substantially perpendicular to the plane of the sheet.
The present invention further improves upon the subject of conductive compositions by providing for the further capability of being able to dissipate heat therefrom. This is a highly valuable advantage because, as known in the art, the conductive electrical energy lost in conduction, i.e. resistance, is converted to heat energy. The present invention provides for a system to remove or dissipate the heat from the conductive composition, thereby resulting in a more efficient and effective interconnector system. The unique features of this invention will become mare apparent from the description which follows.